Disk drives are widely used in computers and data processing systems for storing information in digital form. These disk drives commonly use one or more rotating magnetic storage disks to store data. Each storage disk typically includes a data storage surface on each side of the storage disk. These storage surfaces are divided into a plurality of narrow, annular, regions of different radii, commonly referred to as “tracks”. Typically, an E-block having one or more actuator arms is used to position a data transducer of a transducer assembly proximate each data storage surface of each storage disk. An actuator motor is used to provide a driving force for moving the E-block relative to the storage disks.
Most disk drives are longitudinal recording drives. A longitudinal recording drive records data longitudinally in the tracks of the storage disks. Recently, however, attempts have been made to develop perpendicular recording drives. In contrast to longitudinal recording drives, perpendicular recording drives record data perpendicular to the disk surface of the storage disk. It is anticipated that perpendicular recording drives can more densely record data than longitudinal recording drives. Moreover, perpendicular recording drives are expected to be more thermally stable than longitudinal recording drives.
Typically, during operation of the disk drive, the distance between the data transducer and the storage surface is extremely small, i.e. on the order of microns or less. Accordingly, in order to avoid data transfer errors, the data transducer must be accurately positioned relative to the storage surface. Because of the need for precise positioning of the data transducers relative to the data storage surfaces, and because the storage disks are often magnetic in nature, any extraneous magnetic fields can adversely impact the ability of the disk drive to precisely and accurately read data from the storage disks, and write information to the storage disks. This effect is particularly apparent when the external magnetic field is “vertical”, i.e. perpendicular to the storage surface of the storage disk, or “circumferential”, i.e. substantially parallel to the storage disks and substantially perpendicular to a line drawn from the center of a disk spindle to the data transducer.
One indication of the incidence of error in the transfer of data between the data transducer and the storage disk is known as the “Bit Error Rate”. The term “Bit Rate Error” refers to a number of errors divided by the number of bit transfers. Typically, as the external magnetic field around the disk drive increases, the “Bit Error Rate” of the disk drive increases. Thus, as the Bit Error Rate rises, a higher percentage of inaccuracies occur during operation of the disk drive.
External magnetic fields can influence both longitudinal recording drives and perpendicular recording drives. For example, external magnetic forces can cause transition shifts in perpendicular recording drives. Transition shifts are slight, yet significant timing deviations in the operation of a disk drive. These transition shifts are highly problematic in magnetic storage devices because they alter the ability of the disk drive to accurately and efficiently transfer data to and from the storage disk.
Moreover, the accurate and stable positioning of each transducer assembly near each data storage surface is critical to the transfer and retrieval of information from the magnetic storage disks. External magnetic fields may cause errors in data transfers due to even slight inaccuracies in the positioning of the data transducers during disk drive operation.
In light of the above, a need exists to provide a disk drive that accurately and precisely transfers data to and from a data storage surface of a magnetic storage disk. In addition, there is a need to decrease or inhibit external magnetic forces from negatively influencing operation of the disk drive. Further, the need exists to provide a magnetically stable environment for the disk drive and the internal components of the disk drive. Yet another need exists to provide a disk drive that is not influenced by external magnetic fields, which is relatively easy and inexpensive to manufacture.